The increased concern over the environment and the increased use of chemical information in clinical diagnosis has led to heightened interest in a practical device for trace organic analysis. Analysis of volatile organics is now nearly a routine matter due to the availability of capillary column gas chromatography, particularly when the same is interfaced to mass spectrometers. However, species of organic molecules which are not volatile enough for gas chromatography remain beyond the limits of prior detectors. High performance liquid chromatography (hereinafter HPLC), in practice, did not offer an alternative to analysis of the non-volatile organics. Prior HPLC systems either lacked a sufficient resolution during relatively high speed analysis or required hours to provide adequate data. The corresponding liquid chromatography-mass spectrometer interface also has many difficulties remaining.
Furthermore, the limitations of optical detectors for HPLC are many. Organic molecules lacking convenient absorption bands generally limited HPLC to analysis of unsaturated compounds. Even the far ultraviolet and Fourier Transform infrared detectors are constrained by the possible choice of eluents. Similarly, refractive index detectors generally lack sensitivity and selectivity, particularly when gradient elution is needed for proper separation of test samples. Chemical derivatization to overcome some difficulties, either before or after separation, could improve results, but again convenience and reliability are degraded.
Flame ionization and cation exchange resins have also been used for analysis, but this combination lacks sensitivity. Paper chromatography provides qualitative information in a reasonable time, but even semi-quantitative results are difficult to obtain at low concentration levels.
Since conformation is so specific a property for biological processes, many important clinical and environmental samples involve optically active molecules. Further, most eluents are not optically active. Accurate determination of the optical rotary powder of a sample can provide information regarding its isomeric purity and can provide quality control in pharmacological and food related industries. Thus, an HPLC detector based on optical activity would possess many advantages in the problematic areas of organic analysis. But, prior instrumental limitations have not allowed extension of this principle to micro and trace analysis. Attempts have been made to use optical activity to monitor column chromatography. Again, however, the extension to HPLC was not achieved due to the many technical difficulties associated with operating at the limit of detectability.
Accordingly, it is a principal object of the present invention to provide an apparatus which can analyze trace and microlevels of organic molecules which are not volatile enough for gas chromatography.
A further object of the present invention is to provide a micro-polarimeter for an HPLC which can provide micro and trace level analysis of optically active organic molecules in a relatively short period of time.
A still further object of the present invention is to provide a micro-polarimeter for an HPLC which is reliable and economical to use.